1. Field of the Invention
The present invention relates to en ATM (asynchronous transfer mode) transmission system for transmitting cell-formatted data in an asynchronous transfer mode, and more specifically to an ATM transmission system capable of conducting an online path route test to check easily the validity of a path route in a system.
2. Description of the Related Art
In a transmission system for transmitting data using ATM cells, data are contained in an ATM cell having a limed length of 53 bytes. The header of the ATM cell is provided with a virtual path identifier (VPI) and a virtual channel identifier (VCI) at its initial portion, and applied to a switching unit in the transmission system. In the transmission system, the data are switched using switching information corresponding to the values of the VPI and VCI, and then transmitted to a receiver of the data.
In conducting a path route test on such an ATM transmission system, there has been a problem that it is very difficult to determine externally whether or not an ATM cell transmitted from a subscriber is being transmitted through a path specified by the software. Another problem with the conventional system is that a cell itself or a transmission error can be hardly located during the transmission at the debugging of the system.